While making a simple applied frame for a mirror, I had to flush trim an edge to the main frame face. Duh, how easy?! Thing is, I didn't notice that one piece to flush had a crack in it. The second the router bit hit it, a pretty large chunk splintered off. This is how I fixed it, which didn't look as good in the end as I hoped, but I'll tell ya afterwords how it could have been done correctly.
Basically, I made a kind of bent lamination of the strips into the recess. You'll see that the frame and these strips have a lot of sapwood in them. I really don't care about the sapwood as I'll equalize it with dye then stain and glaze it with General Finished Black Walnut to match an existing vanity... though it makes this repair look bad later :)
How to do it better if you are clear coating? Well, for one, I would have picked thin slices that were all heartwood so they would have a consistent color. Second, depending on whether or not all sides of the repair are visible, I might consider laying shorter slices deep in the recess then top with one that will form the entire visible portion of the repair. This method, though, might show small voids on the side facing you in the picture and that may not be what your project can tolerate. In my case, that side is the side mounted to a wall a could easily tolerate small voids to make a better show side.
Best repair? Notice the crack beforehand and hit it with cyanoacrylic...